Production of nitriles



Patented Oct. 5, 1948 umTEo STATES PATENT OFFICE PRODUCTION OF lN'I'lItILlilfi William 1. Benton, Woodbury,

Bishop, Haddonfleld,

and Richard B.

N. .L, assiznors to Sudan!- Vacuum Oil (loniipany, Incorporated, a corporatlon of New Yor No Drawing. Application January 31, 1946, Serial N0. 644,858 7 9 Claims. (ci. 200-405) This invention relates to a process for producing nitriles having at least two carbon atoms. and is more particularly concerned with a catalytic process for producing nitriles having at least two carbon atoms, from cyclo-parafllnic hydrocarbons.

Nitriles are organic compounds containing I combined nitrogen. Their formula may be represented thus: RCEN, in which R is an alkyl or an aryl group. These compounds are 'very useful since they can be converted readily to many valuable products such as acids, amines, aldehydes. esters, etc. I

As is well known to those familiar with the art, several processes have been proposed for the preparation of nitriles. In general, however, all of these processes have been disadvantageous from one or more standpoints, namely, the relatively high cost of the reactants employed and/or the toxic nature of some of the reactants and/or the number of operations'involved in their ultimate preparation. For example, aliphatic nitrileshave been synthesized by oxidizing hydrocarbons to acids followed by reacting the acids thus obtained with ammonia in the presence of silica gel. Other methods involve reacting alkyl halides with alkali cyanides, reacting ketones withhydrogen cyanide in the presence of dehydration catalysts, etc. Aromatic nitriles have been synthesized by reacting alkali cyanides with aromatic sulfonates or with aromatic-substituted alkyl halides; by reacting more complex cyanides such as potassium cuprous cyanide, with diazonium'halides; by reacting isothiocyanates with copper or with zinc dust; and

-byreacting aryl aldoximes with acyl halides.

We have now found .a process for producing nitriles which is simple and inexpensive, and

which employs non-toxic reactants.

we have discovered that nitriles containing at least two carbon atoms, can be prepared by reacting cycloparaiiinic hydrocarbons with ammonia, at elevated temperatures, in the presence of catalytic material containing molybdenum oxide or tungsten oxide.

Our invention is to be distinguished from the conventional processes for the production of hydrogen cyanide wherein carbon compounds, such as carbon monoxide, methane, and benzene, are reacted with ammonia at elevated temperatures in the presence of alumina, nickel, quartz, clays, oxides of thorium and ceri copper, iron oxide,

silver, iron, cobalt, chromium, aluminum phosphate, etc. The process of the present invention is also to be distinguished from the processes of Another object is to aflord a catalytic process for vantages of the present the gaseous the prior art for the production of amines wherein hydrocarbons are reacted with ammonia at high temperatures, 'or presence of nickel. Accordingly, it is an object of the present invention to provide aprocess for the production of nitriles containing at least two carbon atoms.

the production of, nitriles containing at least two carbon atoms. I Animportant object is to provide a'process for at least two carbon atoms which is inexpensive and commercially feasible. A specific object is to provide a process for producing nitriles containing' at least two carbon atoms, from cycloparamnic hydrocarbons. Other objects and adapparent to those skilled in the art from the following description.

Broadly stated, our invention provides an inexpensive and commercially feasible process tor the production of nitriles containing at least two use the methyl-substituted cycloparaiiinic hydrocarbons, and of. these, dimethyl cyclohexane. methyl cyclohexane and methyldecalin are especially preferred. It will be clear from the discussion of reaction temperatures set forth hereinafter, that many of the aforementioned cycloparailinic hydrocarbons are not when-in contact with ammonia and-a catalyst of the type used herein, for many of them are cracked to related hydrocarbons under such conditions. Nevertheless, all the aforementioned cycloparafllnic hydrocarbons and their hydrocarbon decomposition. products. which are in the vapor phase under the herein-defined reaction conditions serve the purpose of the present invention. It is to be understood also, that hydrocarbon mixtures containing one or more of the aforementioned cycloparanlnicbydrocarbons may also be used herein, andat lower temperatures in the producing nitriles containing invention will become I the hydrocarbon reactant in the proccyclobutanes and cyclopentanes:

.present .per se that when such mixtures are used, the reaction conditions, such as contact time, will be slightly different in view of the dilution effect of the constituents present with the said cycloparaillnichydrocarbon or hydrocarbons. Accordingly, any of the aforementioned cycloparaflinic hydrocarbons, mixtures, thereof, and hydrocarbon mixtures containing one or more of said oycloparamnic hydrocarbons may be used.

The proportions of reactants, i. e., cycloparafilnic hydrocarbon and ammonia, used in our process maybe varied over a wide range with little effect on the conversion per pass and ultimate yield. In general, the charge of reactants may contain as little as 2 mol. or as much as 98 mol.

% of cycloparafllnic hydrocarbons. In practice, however, we use charges containing between about 20 mol. and about 90 mol. of cycloparaflinic hydrocarbon, and ordinarily, we prefer to use charges containing a molar excess of ammonia over the cycloparafflnic hydrocarbon reactant.

We have found that the catalysts to be used to produce nitriles containing at least two carbon be clearly understood that when we speak of molybdenum oxide or of tungsten oxide herein and in the claims, we have reference to the various oxides of molybdenum and tungsten. While all of these metal oxides are operative in the present process, they are not equivalent in their effectiveness from the standpoint of catalytic activity, tungsten dioxide (W02), for example, being far less effective than molybdenum trioxide (M003) the latter being the preferred starting catalytic material.

While these metal oxides exhibit different degrees of effectiveness when used per se, they generally possess additional catalytic activity when used in conjunction with the well known catalyst supports, such as alumina, silica gel, carborundum, pumice, clays. and the like. We especially prefer to use alumina (A1203) as a catalyst support, and wehave found that a catalyst comprising molybdenum trioxide supported on alumina is particularly useful for our purpose. Without any intent of limiting the scope of the present invention, it is suspected that the enhanced catalytic activity of the supported catalysts is attributable primarily to their relatively large surface area.

The concentration of catalytic metal oxide in the supported catalysts influences the conversion per pass. In general, the conversion per pass increases with increase in the concentration ,of metal oxide. For example, we have found that a catalyst comprising 20 parts by weight of molybdenum trioxide on 80 parts by weight of alumine is more effective than one comprising parts by weight of molybdenum trioxide on 90 parts by weight'of alumina. It is to be understood, however, that supported catalysts containinglarger or smaller amounts of catalytic metal oxides may be used in our process.

should be conditioned prior to use in the process. As defined herein, conditioned catalysts are those which have been exposed to ammonia or hydrogen, or both, for a period of time, several minutes to several hours, depending upon the quantity, at temperatures varying between about 800 F. and about 1300* F. However, if desired, the conditioning treatment may be dispensed with inasmuch as the catalyst becomes conditioned during We have found also that in order to obtain initial maximum catalytic efficiency, particularly where the catalytic material comprises the higher catalytic metal oxides, that the catalysts the initial stages of our process when the catalyst comes in contact with the ammonia reactant.

In operation, the catalysts become fouled with carbonaceous material which ultimately affects their catalytic activity. Accordingly, when the emciency of the catalyst declines to a point where further operation becomes unconomical or disadvantageous from a practical standpoint, the

catalysts may be regenerated, as is well known in the art, by subjecting the same to a careful oxidation treatment, for example, by passing a stream of air or air diluted with flue gases over i the catalyst under appropriate temperature conditions and for a suitable period of time, such as the same period of time as the catalytic operation. Preferably, the oxidation treatment is followed by a purging treatment, such as passing over the catalyst a stream of purge gas, for example, nitrogen, carbon dioxide, hydrocarbon gases, etc.

The reaction or contact time, i. e., the period of time during which a unit volume of the reactants is in contact with a unit volume of catalyst, may vary between a fraction of a second and several minutes. Thus, the contact time may be as low as 0.01 second and as high as 20 minutes.

We prefer to use contact times varying between 0.1 second and one minute, and more particularly,

contact times varying between 0.3 second and 30 seconds. i

In general, the temperatures to be used in our process vary between about 850 F. and up to the decomposition temperature of ammonia (about l250-1300 F), and preferably, temperatures varying between about 925 F. and about 1075 F. The preferred temperature to be used in any particular operation will depend upon the,

nature of cycloparatlinic hydrocarbon reactant used and upon the type of catalyst employed. Generally speaking, the higher temperatures increase the conversion per pass but they also increase the decomposition of the reactants thereby decreasing the ultimate yields of nitriles. Accordingly, the criteria for determining the optimum temperature to be used in any particular operation will be based on the nature of the cycloparafiinic hydrocarbon reactant, the type of catalyst, and a consideration of commercial feasibility from the standpoint of striking a practical balance between conversion per pass and losses to decomposition.

The process of the present invention may be carried out at subatmospheric, atmospheric. or superatmospheric pressures. Superatmospherio pressures are advantageous in that the unreacted charge materials condense more readily. Subatmospheric pressures appear to favor the reactions involved since the reaction products have a larger volume than the reactants, and hence, it is evident from the law of Le Chatelier-Braun that the equilibrium favors nitrile formation more at reduced pressures. However, such pressures reduce the throughput of the reactants and preent increased difficulties in recycling unreacted charge materials. Therefore, atmospheric pressure or superatmospheric pressures are preferred.

At the present time, the reaction mechanism in volved in the rocess of the present invention is not fully understood. Fundamentally, the simplest possible method of making nitriles is to introduce nitrogen directly into the hydrocarbon reactant molecule, thereby avoiding intermediate steps with their accompanying increased cost. In our process, we have noted that considerable amounts of hydrogen are evolved and that aliphatic nitriles as well as aromatic nitriles are formed. Hence, it is postulated without any intent of limiting the scope of the present invention, that in our process, the aliphatic nitriles are formed by an initial ring opening followed by replacement by hydrogen with nitrogen, while the aromatic nitriles are formed by the dehydrogenation of a cycloparafiinic hydrocarbon reactant to form an aromatic hydrocarbon, followed by introduction of nitrogen therein.

The present process may be carried out by making use of any of the well-known techniques for operating catalytic reactions in the vapor phase effectively. By way of illustration, methyl cyclohexane and ammonia may be brought together in suitable proportions and the mixture vaporized in a preheating zone. mixture is then introduced into a reaction zone containing a catalyst of the type defined hereinbefore. The reaction zone may be a chamber of any suitable type useful in contact-catalytic operations; for example, a catalyst bed contained in a shell, or a shell through which the catalyst flows concurrently, or countercurrently, with the reactants. The vapors of the reactants are maintained in contact with the catalyst at a predetermined elevated temperature and for a predetermined period of time, both as set forth hereinbefore, and the resulting reaction mixture is passed through a condensing zone into a receiving chamber. It will be understood that when the catalyst flows concurrently, or countercurrently, with the reactants in a reaction chamber, the

The vaporized tionis taking place in one or more of the reaction chambers, regeneration of the catalyst will be taking place in one or more of the other reaction chambers. correspondingly, the process may be continuous when we use one or more catalyst chambers through which the catalyst flows in contact with the reactants. In such a continuous process, the catalyst will flow through the reaction zone in contact with the reactants and will thereafter be separated from the reaction mixture as, for example, by accumulating the catalyst on a suitable filter medium, before condensing the reaction mixture. In acontinuous process, therefore, the catalyst-fresh or regenerated and the reactants-fresh orrecycle-will continuously flow through a reaction chamber.

The following detailed examples are for the purpose of illustrating modes of preparing nitriles in accordance with the process of our invention, it being clearly understood that the invention is not to be considered as limited to the specific cycloparafllnic hydrocarbon reactants and catalysts disclosed therein or to the manipulations and conditions set forth in the examples. As it will be apparent to those skilled in the art, a wide variety of other cycloparaillnic hydrocarbons and 1 of other catalysts of the type described hereinbefore may be used. I

A reactor consisting of a shell containing a catalyst chamber heated by circulating a heattransfer medium thereover, and containing 100 parts by weight of catalyst by weight of molybdenum trioxide supported on 90 parts by weight of activated alumina was used in the run of Example No. 1, while in the run of Example No; 2, the 100-parts by weight of catalyst catalyst will be thereafter suitably separated from the reaction mixture by filtration, etc. The reaction mixture will be predominantly a mixture of nitriles, hydrogen, toluene, unchanged methyl cyclohexane, and unchanged ammonia. The nitriles, the unchanged methyl cyclohexane, and toluene will be condensed in passing through the condensing zone and will be retained in the receiving chamber. The nitriles can be separated from the unchanged methyl cyclohexane and toluene by any of the numerous and well-known separation procedures, such as fractional distillation. Similarly, the uncondensed hydrogen and unchanged ammonia can be separated from each other. The unchanged methyl cyclohexane and ammonia, and toluene, if desired, can be recycled, with or without fresh methyl cyclohexane and ammonia, to the process.

comprised 20 parts'by weight of molybdenum trioxide supported on 80 parts by weight of activated alumina. The catalyst was prepared by soaking commercial activated alumina in an aqueous solution of ammonium molybdate, followed by heating of the thus treated alumina to, drive of! ammonia and water. The catalyst was conditioned by passing a stream of ammonia thereover for 45 minutes at 900 F. Ammoniaand various cycloparafilnic hydrocarbons, in a molar ratio of 2:1, respectively, were introduced in the vapor phase into the reactor. The reaction mixture was passed from the reactor, through a condenser, into a first receiving chamber. Hydrogen and unchanged ammonia were collected in a second,receiving chamber and then separated from each other. The nitriles and the unchanged cycloparafllnic hydrocarbon reactants (some of the latter were converted to" aromatic hydrocarbons) remained in the first receiving chamber. and were subsequently separated by distillation.

The pertinent data and the results of each run are tabulated in the following table:

Example No.

lo car Conversion Per Pass Per Cent Wt. oi

ydrocarbon Charged Tem- Contact Time In Seconds on Reactant ture in F.

methyl cyclohexane.

dimethyl cyclohexane- Benzonitrilel Tolunitrile. Acetonitrile.

It will be apparent that the process may be perated as a batch or discontinuous process as y using a catalyst-bed-type reaction chamber in which the catalytic and regeneration operations .lternate. With a series of such reaction chamers, it will be seen that as the-catalytic opera- 7 as intermediatesin organic syn .siderable value in making It will be apparentthat the present invention provides an efllcient, inexpensive and safe process for obtaining nitriles. Our process is of conavailable relatively inexpensive nitriles which are useful, for example,

comprising 10 parts Formed f i oxide.

success This application is a continuation-in-part oi copending application, Serial Number 39,032, filed June 6, 1944, now abandoned.

Although the present invention has been described in conjunction with preferred embodiments. it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as thoseskilled in the art will readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.

We claim:

1. A process for the production of nitriles having at least twocarbon atoms per molecule, which comprises contacting acycloparaiilnic hydrocarbon selected from thegroup consisting of dimethyl cyclohexane, methyl cyclohexane, and methyl decalin, with ammonia, in vapor phase, at temperatures falling within the range varying between about 925 F. and about 1075 1"., in the presence of a catalyst comprising a molybdenum 2. A process for the production nitriles having at least two carbon atoms per molecule, which comprises contacting a cycloparafllnic hydrocarbon selected from the group consisting oi dimethyi cyciohexane, methyl cyclohexane, and methyl decalin, with ammonia, in vapor phase, at temperatures falling within the range varying between about 925 F. and about 1075" E, in the presence of a molybdenum oxide supported on a catalyst support. I

3. A process for the production of nitriles having at least two carbon atoms per molecule, which comprises contacting a cycloparamnichydrocarbon selected from the group consisting of dimethyl cyclohexane, methyl cyclohexane, and methyl decalin, with ammonia, in vapor phase, at temperatures falling within the range varying between about 925 F. and about 1075" R, in the presence of molybdenum trioxide supported on alumina.

4. A process for the production of nitriles having at least two carbon atoms per molecule, which comprises contacting methyl cyclohexane with ammonia, in vapor phase, at temperatures falling within the range varying between about 925 F. and about 1075 F., in the presence of a catalyst comprising a molybdenum oxide.

5. A process for the production of nitriles hav- 8 ing at least two carbon atoms per molecule, which comprises contacting methyl cyclohexane with ammonia, in vapor phase, at temperatures falling within the range varying between about 925 F. and about 1075 F., in the presence of a molybdenum oxide supported on a catalyst support.

6. A process for the production or nitriles having at least two carbon atoms per molecule, which comprises contacting methyl cyclohexane with ammonia, in vapor phase, at temperatures falling within the range varying between about 925 F. and about 1075" F., in the presence oi molybdenum trioxide supported on alumina.

7. A process for the production of nitriles having at least two carbon atoms per molecule, which comprises contacting dimethyl cyciohexane with ammonia, in vapor phase, at temperatures taliing within the range varying between about 925 1?. and about 1075 F., in the presence of a catalyst comprising a molybdenum oxide.

* 8. A process for the production of nitriles having at least two carbon atoms per molecule, which comprises contacting dimethyi cyclohexane with ammonia, in vapor phase, at temperatures laliing within the range varying between about 925 F. and about 1075 F., in the presence of a molybdenum oxide supported on a catalyst support.

9. A process for the production of nitriles having at least two carbon atoms per molecule, which comprises contacting dimethyl cyclohexane with ammonia, in vapor phase, at temperatures falling within the range varying between about 925 F. and about 1075 FL, in the presence of molybdenum trioxide supported on alumina.

WILLIAM I. DEN'ION. RICHARD B. BISHOP.

. REFERENCES GKTED The following referencesare of record in the 40 file of this patent:

UNITED STATES PATENTS apg et al Aug. '1, 194: 

